Europe’s largest floating power station is near completion. When the £6.5m solar farm goes fully online, it will help power water treatment works on the outskirts of London.

But its existence depended on beating a deadline on a government cuts to solar subsidies.

Nick Boyle is the CEO of Lightsource, which built the installation and will sell the electricity it generates to Thames Water. He told Sky News: “The panels and the wires work optimally at a cooler temperature. One of the biggest advantages here is the water keeps the panels cool, keeps the wires cool, and actually increases the efficiency of the installation. Plus in an area such as this – this is built up London – space is at a premium, and this is utilising space that wasn’t being utilised for anything else than water treatment, which it can still do.”

Each panel is mounted onto an air-filled float, which are joined together to make rafts. Deep divers have fixed 177 anchors to the bottom of the reservoir and cables carry the power ashore and onto the treatment centre a few kilometres away.

Floating solar farms are becoming popular wherever things are a bit cramped. Japan already has one water based solar plant and is currently building the world’s biggest. The first was built in the UK in 2014, in Berkshire, and another is under construction in Manchester.

“This plant will qualify for the renewable obligations certificate,” said Mr Boyle in an interview. “But in order to do that, it had to be built by the 31 March 2016. If this was being built a day after that – or being connected a day after that – it wouldn’t be possible.”

Others argue that after a period of generous subsidy, solar technology should be able to stand on its own two feet. Douglas Stewart, the CEO of Green Energy UK says, “There are two sides to this. One is you need to kick-start the industry. You need to put incentives into place to get people to take risks. But by the same token, you can’t burden the public with the costs associated with it. And tariffs are passed onto the public.”